A fresh and engaging examination of our physiological history reveals how many of our diseases actually helped our ancestors survive environmental crises. When the option is a long life with a disease or a short one without it, evolution usually opts for disease.

WHAT THE CRITICS ARE SAYING:

"Moalem's approach to these questions is solidly rooted in evolutionary theory, and he capably demonstrates that each disease confers a selective advantage to individuals who carry either one or two alleles for inherited diseases.... his light style makes for easy reading for readers new to this subject." -- Publishers Weekly

"A lively and enthusiastic treatise" -- Kirkus Reviews

ABOUT THE AUTHOR:

Sharon Moalem holds a doctorate in physiology and neurogenetics and evolutionary biology. He is finishing his medical training to become a doctor. He hopes both to practice medicine and conduct further research.Jonathan Prince was a Clinton White House adviser and speechwriter.

A CONVERSATION WITH THE AUTHOR:

Pop quiz: Can a person rust to death? Can wearing sunglasses lead to more sunburn than you'd have without them? Is it true many Asians can't tolerate alcohol? The answer is yes to all of the above, as Sharon Moalem explains in his book, on the Today Show and anywhere else that will have him where he can discuss his passionate investigations into things medical. I manage to get him one on one in his Little Italy apartment in New York City.

"Your thinking seems to involve a tremendous number of cross associations. Has your brain always been wired that way?

"Yes, ever since I was a little child."

"Your regular reading must include some strange periodicals and books."

"What I like to do is to find a book on a topic I know nothing about. This makes for a very strange library that I've amassed over the years. Likewise, with magazines, I'm drawn to the ones I've never encountered before. I was just reading a book by a general about strategies in the Middle East conflicts, for instance, which gave me the idea of applying modern warfare techniques to the workings of certain infectious diseases. The principles must be universal, I thought, because they are about survival. How armies fight, or individuals sometimes struggle against one another, has parallels in the microscopic world. There are certain bacteria, for example, that when they sense their time is over and they're going to be overwhelmed by the body's forces, they commit suicide essentially, they blow up. And when they do that they release toxic enzymes -- kind of like a suicide bomber -- intended to kill your cells. They want to go down fighting."

"It's their last shot at you."

"Yeah."

"I've read that microbial life that's invaded you and replicating waits until it reaches critical mass, then it signals back and forth, one to the other, to launch the assault. Is this true?"

"Yes, though in a slightly different way. Viruses are a lot more about guerrilla warfare and terrorism -- insurgency. They're sneaky. They will wait until the body's defenses are down before they launch an attack. The virus detects that the immune system is depressed and then it will launch its assault. It lurks, waiting for the exact right moment."

"But this implies that they're sentient beings, these inert chemical entities. Which challenges the conventional definitions of life, no?"

"To some degree they are aware, and yes, it challenges the definition of life completely."

"What are frogsicles?"

Sharon Moalem laughs heartily. "Frozen frogs. There's an amazing amphibian, the wood frog. It has an astonishing ability to freeze solid every winter. It's brain stops; its heart stops. And it does this by becoming diabetic. Its sugar levels spike a hundred times normal when it senses the cold taking hold. The increased sugar acts like a natural antifreeze. The wood frog manages itself into a frozen, suspended state, then reverses this after the winter and resurrects, comes back to life."

"So if we could figure out how to freeze human organs without damaging the tissues, we could preserve them for transplants"

"Exactly. The wood frog suggests that diabetes may have helped early European residents to endure the sudden cold of a small ice age."

"And like a good many discoveries in science, this one was also accidental."

"Yeah. Dr. Ken Storey, a researcher, discovered this when he inadvertently froze his wood frogs solid in the trunk of his car. He just forgot them there. I wish I could have been a fly on the wall when he brought them into his lab to dissect the dead frogs, only to have them jumping around as they thawed out."

"Your grandfather liked to donate blood quite regularly. Did the medical mystery around your grandfather lead you into this work?"

"Definitely. And to question how doctors come up with their diagnoses and why particular illnesses exist. My grandfather was doing something that simply made him feel better, made his aches go away -- giving up some of his blood. If he'd told a doctor that, the doctor would've laughed at him."

"He suffered from a dangerous accumulation of iron: hemochromatosis."

"Yes, he was rusting to death. Too much iron damages organs. When he came down with Alzheimer's later, I thought there could be a link with the excessive iron in his body."

"You were 15."

"Yes. I went to college, studied biology, then neurogenetics. And after two years of research, the connection was made -- a genetic association."

"Is it a rare condition?"

"No, common, one of the most common genetic disorders in descendants of Western Europeans. Including me."

"So why the disease?"

"It was probably a protection against a worse illness: the plague. People with my condition mostly survived the bubonic plague and passed it on to their children. That's the theory. People with hemochromatosis lock away iron and their bodies think they don't have enough and absorb more continuously. Iron helps almost all bacteria, fungi, and protozoa multiply. Parasites hunt us for our iron. Cancer cells thrive on it. Systems suffering with hemochromatosis mislead these organisms into believing the iron isn't there, or isn't available. So the plague passes them up. Similarly, males have more iron than women and so male plague victims outnumber female victims two to one."